Apparatus for supporting a stack of sheet material being cut or otherwise worked on

ABSTRACT

Apparatus for supporting a stack or layup of air-impervious sheet material to be cut or otherwise worked upon includes a horizontal base on which the stack is positioned. The stack is covered by an air-impervious cover sheet, and by as associated vacuum means, air is withdrawn from between the top of the stack and the cover sheet to create a sub-atmospheric pressure under the cover sheet whereby atmospheric pressure on the top of the cover sheet will hold the stack in a firm condition while it is worked upon by a cutting tool or the like. The means for withdrawing air from between the cover sheet and the top of the stack includes a porous or air conducting layer of material, such as corrugated cardboard, which may be part of the cover sheet or a separate sheet in itself. If the material of this stack includes layers of porous material alternating with layers of air-impervious material, the latter porous layers themselves serve as air-conducting layers for withdrawing air from below the cover sheet and from between the layers of air-impervious material of the stack. Preferably, to provide the vacuum means, the horizontal base for supporting the stack is air-pervious and located over a vacuum chamber with the vacuum from the chamber passing through the horizontal base and past the longitudinal edges of the stack, through a block or layer of air conducting material, to the space between the cover sheet and the top of the stack.

United States Patent [191 Gerber Dec. 11, 1973 APPARATUS FOR SUPPORTING A STACK OF SHEET MATERIAL BEING CUT OR OTHERWISE WORKED ON [75] Inventor: Heinz Joseph Gerber, West Hartford, Conn.

[73] Assignee: Gerber Garment Technology, Inc.,

East Hartford, Conn.

[22] Filed: Apr. 25, I972 [21] Appl. No.: 247,468

' Related U.S. Application Data [63] Continuation of Ser. No. 91,965, Nov. 23, 1970,

[56] References Cited UNITED STATES PATENTS 3,495,492 2/1970 Gerber et al. 83/925 CC 3,585,888 6/1971 Wiatt 831925 CC Primary Examiner-L M. Meister Attorney-McCormick et al.

[57] ABSTRACT Apparatus for supporting a stack or layup of airimpervious sheet material to be cut or otherwise worked upon includes a horizontal base on which the stack is positioned. The stack is covered by an airimpervious cover sheet, and by as associated vacuum means, air is withdrawn from between the top of the stack and the cover sheet to create a sub-atmospheric pressure under the cover sheet whereby atmospheric pressure on the top of the cover sheet will hold the stack in a firm condition while it is worked upon by a cutting tool or the like. The means for withdrawing air from between the cover sheet and the top of the stack includes a porous or air conducting layer of material, such as corrugated cardboard, which may be part of the cover sheet or a separate sheet in itself. If the material of this stack includes layers of porous material alternating with layers of air-impervious material, the latter porous layers themselves serve as air-conducting layers for withdrawing air from below the cover sheet and from between the layers of air-impervious material of the stack. Preferably, to provide the vacuum means, the horizontal base for supporting the stack is airpervious and located over a vacuum chamber with the vacuum from the chamber passing through the horizontal base and past the longitudinal edges of the stack, through a block or layer of air conducting material, to the space between the cover sheet and the top of the stack.

28 Claims, 11 Drawing Figures PAIENIEDuEc 1 i ma 3.777.604

sum 1 [BF 3 INVENTOR HEINZ JOSEPH GERBER ATTORNEYS PATENIEDnsc 11 m5 3.777.604

SHLET 3n; 3

FIG. 8

APPARATUS FOR SUPPORTING A STACK F SHEET MATERIAL BEING CUT OR OTHERWISE WORKED ON This 7 is a continuation, of application Serial No. 91,968, filed Nov. 23, 1970, now abandoned.

BACKGROUND OF THE INVENTION pends upon the capability of the apparatus for holding the sheets against relative movement irrthestack while the cutting operation is performed.

Our prior U. S. Pat. No. 3,495,492, issued Feb. 17, 1970, discloses an apparatuswherein the sheets or layers in the stack are supported on a vacuum table or base, and the stack is covered by arthin, air-impervious sheet so that the vacuum force will withdrawair from the stack and thus create a subatmospheric pressure under the cover sheet. In this arrangement, atmospheric pressure acting on the outside of the cover sheet holds the stack quite rigidly, almost likeablock, and there is substantially no relative movement between the sheets or layers in the stack. i

The apparatus of the patent is particularly effective when the layers or plies in the stack are-ofperviousmaterial, as is the case in cutting fabrics. The apparatusis less effective in holding the stack as desired when the sheets or plies thereof, or at.least some of them, are'airimpervious such as is the case in cutting plastic sheets or the like.

Accordingly, it is the general objectof the present-invention to provide a means of holding a stack ofsheet material including impervious sheets on a vacuum hold-down apparatus of the type shown in the aforesaid patent so that the sheets are firmly held against relative movement during the cutting operation .or any other work operation performed thereon.

SUMMARY OF THE INVENTION Apparatus provided according to this invention com prises a base having a supporting surface upon which a stack of sheet material can be placed for cutting or other operation either by a hand-guided tool or by an automatically controlled tool such as a cutter supported over the base on a carriage capable of longitudinal and transverse movement relative thereto. The type of material with which the invention is employedis edges of the stack, and at such edges vacuum is applied air flow layer is provided by a means for producing a vacuum adjacent the supportingsurface ofthe base and this latter vacuum is conducted through porous blocks or porous layers of material vertically past the side edges of the stack to the horizontal air flow layer. In a more specific form of the invention, the horizontal air flow layer preferably consists of corrugated cardboard or similar means having air channels extending only in the transverse direction relative to the stack and vacuum is applied to only that portion of the horizontal air fiow layerithat is located in the vicinity of the tool used to work on the stack, the zone of vacuum application preferably being controlled by the position of the tool longitudinally of-the stack. The air-impervious cover sheet and the'horizontal air fiow layer may be two separate sheets or part of a signal sheet, and each or both may be spread over the entire extent of the stack or may compriseendless belts located in front and in back of the toolandsuitablysupported on rollers for movement longitudinally of the stack with corresponding longitudinal movement of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 isa fragmentary perspective view of anapparatus provided in accordance with the present invention.

FIG. 2 isan enlarged transverse cross-sectional view showing aportion of the apparatus base and the stack located thereon.

EIGL3 isan enlargedfragmentary perspective view of one form of sheet material upon which the apparatus may be employed.

FIG. 4 is a'view similar to FIG. 2 but showing a modified construction.

FIG. 5 is a further view similar to FIGS. 2 and 4 but showing a further modification of the construction.

FIG. 5A is a fragmentary longitudinal sectional view taken through the apparatus of FIG. Sas indicated generally by the line 5A-5A of FIG. 5.

FIG. 6 is a longitudinal sectional view taken through the base and stack of the apparatus as it is shown in FIGS. 5 and 5A, butillustrating the use of a specific type cutter and cutter tool carriage.

FIG. 7 isa view of the cutter employed in the apparatus at FIG. 6, the view being taken as indicated generally by the line 7--7 of FIG. 6.

FIG. 8 is a further longitudinal sectional view through the apparatus showing a further modification thereof.

FIG. 9 is a view similar to FIGS. 2, 4 and 5 but illustrating the modified form shown in FIG. 8.

FIG. 10 is a still further longitudinal sectional view showing a still further modification of the apparatus.

DETAILED DESCRIPTION OFPREFERRED EMBODIMENTS As indicated in FIG. l, the apparatus provided in keeping with the present invention includes an elongated horizontal table designated generally by the reference number 10. The table 10 includes longitudinally extending vertical side walls 12, 12 :and spaced-apart vertical transverse walls such as the wall 14. The table also includes a bottom wall 16 which is impervious as are the side walls and transverse walls, and it includes an air-pervious top wall or base indicated generally by the refernce number 18. The pervious top wall or base 18 preferably comprises a sheet of perforate metal 20 such as expanded metal lath supported between the vertical side walls and transverse walls or rails such as the rail 22 shown in FIGS. 1 and 2. The pervious wall or base 18 also includes a thick layer or porous, airpervious material 24 supported between the vertical walls 12 and 14 on the metal lath 20. The thick layer of material 24 preferably comprises a resilient lowdensity cellular polyethylene plastic material such as ETI-IAFOAM, a product of Dow Chemical Company. Preferably, the material is provided with a plurality of vertical passages to assist in the relatively free flow of air through the said base material and thus through the underlying expanded, metal lath sheet 20.

The air-pervious horizontal base 18 extending between the impervious vertical walls 12 and 14 in vertically spaced relationship to the impervious bottom wall 16 defines a vacuum chamber below the base which is divided into a plurality of compartments 11, 11, arranged end-to-end along the length of the table, by a plurality of transversely extending impervious walls, one of which is indicated at 13, located between the bottom wall 16 and the expanded metal lath sheet 20. A vacuum duct 15 extends longitudinally of the table below the bottom wall 16 and communicates with each vacuum chamber compartment 11 through a port 17. The port 17 of each compartment is normally closed by a valve 19 biased to a closed position relative to the port 17 by a spring 21, and the valve 17 is movable to its open position by a rod 23 having an outer end portion passing through and beyond the right-hand side wall 12 of the table, as viewed in FIG. 1. Moving each valve operating rod 23 inwardly toward the table 12 opens its associated vacuum port 17 to admit vacuum from the duct 17 to the associated vacuum compartment 11. This is all generally similar to the table disclosed in U. S. Pat. No. 3,495,492 wherein it is explained that when a valve is opened to apply vacuum to its associated vacuum compartment, air is drawn down through the overlying portion or zone of the perforate or porous base 18 to hold the stack of material supported thereon in a rigid condition for purposes of cutting or otherwise working such material.

Also, similarly to the table disclosed in U. S. Patent .3 .425 4 2th? tab et" 9 F .6-. li c an assqs a eq.

means for supporting a cutting tool 28 for movement in two coordinate directions relative to the base. As shown, this means includes a main carriage 30 movablelongitudinally of the table and its material supporting base along side rails 32, 32. In addition, the main carriage includes a sub-carriage 34 which is movable transversely relative to the main carriage and to the table. The tool 28 is part of a cutting head 33 carried by the work carriage 34 and it, in addition to reciprocating and lifting and lowering the tool,,also accommodates angular movement of the cutting tool about its vertical axis. Thus, it can be said that the cutting tool is supported on the apparatus for movement along an X axis longitudinally of the table, for movement along a Y axis transversely of the table, and for angular movement about a vertial 0 axis, which axes are those as indicated in FIG. 1. 7

On its right-hand side, as viewed in FIG. 1, the main carriage 30 has attached thereto a longitudinally extending cam plate 35 positioned to operate the valve operating rods 23, 23. The length of the cam plate 35 I is slightly greater than the spacing between two of the valve operating rods 23, 23, so that for every longitudinal position of the main carriage'30, one or two of the valve operating rods 23, 23 is held in an operated position whereat the associated valve member is opened to; admit vacuum to the associated vacuum compartmen 11. Accordingly, it will be understood that as the main carriage 30 moves longitudinally of the table, the cam plate 35 operates the valve operating rods 23, 23 in such a manner that vacuum is applied to that portion of the porous base 18 which is located in the vicinity of the tool 23. It should be understood, however, that it is not necessary in all instances to divide the table into a number of vacuum compartments, and if desired, in some cases, the space below the porous base 18 may constitute one continuous vacuum chamber so that the entire extent of the porous base is exposed to vacuum at one time.

In FIG. 1, the stack of sheet material which is to be cut by the tool 23 is indicated generally by the letter S. It will be observed that this stack is laid up on the base 18 to extend longitudinally, and it will be seen that the stack is in inwardly spaced relationship to the vertical side walls 12, 12. In the forms of the invention shown in FIGS. 1, 2, 5 and 9, a relatively resilient and relatively non-compressible block of air-pervious material 36 is located between each side of the stack S and the associated vertical side wall 12. The block 36 can be made of a variety of materials which are porous and thus air-pervious, such as glass fibers, foamed plastic, woven fabric, or foamed polyurethane, or any other material capable of being formed with structural integrity into a flexible and relatively non-compressible block. It is the purpose of the blocks 36, 36 to provide passage for the flow or withdrawal of air generally horizontally from the layers in the stack S and then downwardly through the pervious base 18 to the vacuum chamber. In order to confine the flow or withdrawal of air as described, a thin impervious cover sheet 38, which preferably comprises a polyethylene film, is laid over the stack and across the blocks 36, 36 and over the top edges of the impervious side walls 12, 12.

The stack of sheet material S shown in FIGS. 1 and 2 consists of layers of the sheet article shown in FIG. 3. Such sheet article comprises a multi-ply insulating sheet made up of a porous ply of insulating material 40 sandwiched between two metal foil layers 42, 42, each layer or ply 42 being air-impervious When the articles are stacked as shown in FIG. 2, air is withdrawn edgewise from the porous layers 40, 40 and between the airimpervious layers 42, 42. This air then flows through the blocks 36 and the base 18 into the vacuum chamber so that 'atmopsheric pressure on the outside of the cover sheet 38 will exert a holding force against the stack as it is being cut. Obviously, there will be leakage of air from the atmosphere through the cut C (FIG. 1) in the cover sheet 33, but this leakage is not sufficient to prevent the stack being firmly held by the atmospheric pressure. That is, despite such leakage as may occur, a sub-atmospheric pressure exists below the cover sheet 38 so that atmospheric pressure will provide a holding force.

The embodiments shown in FIGS. 4-10 are especially adapted to handle a stack S wherein the sheet material is wholly impervious and includes no layers of porous material. In solving the problem of rigidly supporting such a stack of sheet material it has been found that if air can be withdrawn generally horizontally from the top of the stack and below the film sheet 38 and then directed downwardly at the sides of the stack through the base 18 atmospheric pressure bearing on the top of the stack and at the sides thereof through the cover 38 will hold the sheets in the stack in a relatively rigid condition suitable for cutting or other operations thereon.

This is accomplished in the embodiment shown in FIG. 4 by providing a relatively flexible and relatively non-compressible air-pervious pad or layer 44 spread across the top of the stack and down the sides thereof to the top surface of the base 18. As in the case of the air-pervious block 36 previously described the illustrated pad 44 is or may be made of foamed urethane or other porous plastic foamed material, glass fibers, or any other material having the properties of porosity, flexibility and relative rigidity. It may also consist ofa sheet of semi-rigid or non-compressible material such as corrugated cardboard or embossed plastic sheet, which because of its surface configuration provides airconducting channels between it and the surface against which it is placed. When such a pad is employed as shown in FIG. 4, the air is withdrawn from around the stack, as indicated by the arrows to flow horizontally off the top of the stack and then down the sides thereof and through the base 18. If desired, instead of making the pad 44 and cover sheet 38 of separate sheets of material the two may be bonded together to form a single article. As another alternative, the pad 44 and. cover sheet 38 may be replaced by a single sheet of airimpervious material, such as corrugated cardboard or sheet plastic embossed with a waffleddesign, which includes channels in its surface allowing the passage of air between it and the surface against which it. is pressed however, in this case, it is desirable to close the air conducting channels at the edge of the sheet to prevent the loss of vacuum by the flow of air past such edges.

Another means associated with the cover 38 for per.- mitting a generally horizontal flow of air off of the stack is that shown in FIGS. 5 and 5A. As shown in these two views, such means comprises a relatively noncompressible blanket or layer of material 46 having a body 48 which is corrugated on its bottom side to define a large number of closely spaced flutes or channels 50, 50 which extend transversely across the stack. As best shown in FIG. 5 the blanket 46 extends across the stack S and onto the top of an air-impervious block 36 at each side of the stack. With this arrangement, air is withdrawn horizontally from the stack S through the flutes 50, 50 and then downwardly through the two blocks 36, 36 into the pervious base 18 as indicated by the arrows. The transverse arrangement of the flutes 50, 50 is particularly desirable for use with an apparatus, such as that of FIG. 1, wherein vacuum is applied only to that portion of the porous base. located within the vicinity of the cutting tool. That is, the tranversely extending flutes tend to confine the withdrawal of air from that portion of the stack which is aligned with the vacuum compartments ll, 11 of the table which are opened to the vacuum source. In cases where theentire porous base of the table is exposed to a vacuum at one time, the use of transverse channelsin the blanket 46 is not needed to confine the vacuum to a given .zone and accordingly, if desired, the blanket 46 may be provided on its lower side with a waffle configuration or other design providing channels allowing air flowin stroy the effectiveness of atmospheric pressure bearing down upon the stack to hold it in place. However, the leakage occasioned by such cuts can be minimized by utilizing the construction shown in FIGS. 6 and 7, particularly in cases where as in FIGS. 1, vacuum is applied to the porous base only in the vicinity of the cutting tool.

As shown in FIG. 6, a modified main carriage 30a is provided. to. support the cutter 33. This construction is only schematically illustrated, but it will be seen that the carriage 30a supports a bracket 52 at each longitudinal end thereof which in. turn rotatably supports an endless belt 54 which is entrained over a roller 56 and a nose piece 58. The roller 56 may be driven or freely rotatablymounted on the saddle a so that the lower extent of each. endless belt 54 will engage the cover sheet 38. at the top of the stack to help hold it and the underlying blanket 46 down. Thus, as seen in FIG. 6, there are two endless belts 54, 54 provided one on each longitudinalside of the cutting tool 60. As so arranged, the endless belts 54, 54 will move with the carriage 30a longitudinally of the stack and base or in the X direction as indicated in FIG. 1. These endless belts help to smooth the sheets in the stack and the overlying cover 38 and the blanket 46 and help to prevent the cover and the blanket from being lifted upwardly by vertical reciprocationof the cutting tool 60. They also act to sealzthe cuts made inthe cover sheet 38 by the cutting tool 60and thereby minimize the llossof vacuum and holding power asa result of the cutting process.

Thecutting tool 60 illustrated in FIGS. 6 and 7 comprises an elongatedknife which is to be reciprocated verticallyinthecuttingoperation through the stack S. To further facilitate the hold ,down of the cover sheet '38 andtheunderlying blanket 46, a pair of rollers 62, 62 are rotatably mounted at the lower ends of bracket arms 64, 64-which are resiliently mounted on the lower portion of the cutter 33 so as to rotate with the cutting tool 60 about the vertical axis 0. These rollers press against the cover sheet and underlying blanket immediately adjacent the cutting tool or knife 60 and on the opposed transverse sides thereof. If desired, a foot 66 in the nature of a pressure foot can also be mounted on each roller support arm 64 to ride over the cover sheet 38(andtend to smooth out and hold down any wrinkles orflaps that may develop therein. Preferably, as indicated in FIG. 6, the rollers 62, 62 are so arranged that their common horizontal axis of rotation passes through the verticalaxis O of the cutting tool rotation so that as the cutting tool is rotated, they roll over the cover sheet 38 without any dragging or sliding motion.

It is to be understood that when a blanket constructionlike that shown at 46 is utilized, the cover sheet of plastic film 38 can beeliminated, if desired. For example, if the vertical side walls 12, 12 of the apparatus are 7 extended upwrdly to approximately the height of the stack S and the blocks 36, 36 located alongside the stack, the blanket 46 can be extended to engage the top edge of the said side walls and its flutes closed at the ends. This is illustrated in FIG. 9 wherein a modified blanket 46a is shown. In such blanket, the body portion 48a thereof is formed of an air-impervious material and the flutes 50a formed in the bottom thereof by the corrugations are closed at the transverse end edge portions of the blanket so that air will flow through the said flutes and then downwardly through the pervious blocks 36, 36, as illustrated by the arrows in FIG. 9.

This same sort of flute construction is utilized in the embodiment of the invention shown in FIG. 8 wherein no cover film is employed. As shown in FIG. 8, the blanket material is utilized to form two endless belts 68, 68 which are entrained over rolls 70, 70 rotatably supported on the tool carriage (not shown). These rolls can be either freely rotatable or driven and are supported on the carriage to be moved longitudinally of the apparatus with longitudinal or X axis movements of the cutting blade or tool 60. There is one such endless belt supported on each longitudinal side of the cutting tool and closely adjacent thereto to hold the stack S down by atmospheric pressure bearing upon the lower extent of each endless belt. It will be observed that the belt or blanket 68 is of the type shown in FIG. 9 wherein its flutes are terminated adjacent its transverse edges so that air will flow horizontally and then downwardly as shown by the arrows in FIG. 9.

All of the embodiments heretofore described contemplate the use of a fixed vacuum table or base and the use of a movable tool support carriage. In FIG. 10 a construction is shown wherein the cutting tool is held in a fixed position relative to the X axis and the stack is moved past the cutting tool in the longitudinal direction or along the X axis by a movable base.

More specifically, the cutting tool may comprise a band saw type device such as indicated generally by the reference number 72, the said band saw being supported by a carriage fixed against longitudinal movement but with the saw extending through the stack and downwardly as shown and movable in the transverse direction. In this embodiment, a blanket 46a like that shown in FIG. 9 is employed over the stack and the stack is supported on a generally horizontal base comprising a pair of endless belts 74, 74 supported respectively on rotatable drums such as the drums 76, 76. As shown in FIG. 10, the endless belts move in the same longitudinal direction and they are supported on adjacent drums on opposite longitudinal sides of the cutting tool or band saw 72. The belts 74, 74 aremade of an air-pervious material so that air can be withdrawn through them. Air is withdrawn through the belts at the sides of the stack by means of vacuum chambers 78, 78 located within the drums 76, 76 which are closest to the cutting tool. In this arrangement, the air is withdrawn from the top of the stack through the flutes of the corrugated blanket 46a and then downwardly through the blocks 36, 36 at the sides of the stack and thus through the belts 74, 74 and into the vacuum chambers 78, 78 which are shown to be arranged as closely as possible to the cutting tool on the opposed longitudinal sides thereof.

It is to be understood that an arrangement generally similar to that shown in FIG. 10 can be employed for moving the stack to be cut past a cutting tool of the type shown generally in FIGS. 1, 6, 7 and 8 wherein the cutting tool does not extend below the apparatus. In

such embodiment, a single conveyor belt may be employed to move the stack past the cutting tool with a vacuum chamber defining means located below the belt in the cutting tool area.

Iclaim: v

1. In an apparatus for supporting a stack of sheet material to be worked upon by a tool and having a generally horizontal air-pervious base disposed between generally vertical impervious walls to cover a chamber subjected to vacuum to draw air downwardly through the base, and also having a means supporting a tool over the base for movement relative thereto when working upon a stack supported on the base, an improved structure for subjecting a stack having impervious sheet material to the vacuum force by withdrawing air horizontally from the stack and then downwardly, such structure including an air-impervious cover extending between at least two of the said walls and across the stack, means associated with the cover adjacent the top of the stack to permit generally horizontal air flow in the direction the cover extends across the stack, and an airpervious block disposed between at least one of the said walls and the stack to permit the air being withdrawn horizontally of the stack to be directed downwardly to the vacuum chamber, whereby the stack is firmly supported on the base by air at atmospheric pressure bearing upon the cover.

2. The apparatus improvement set forth in claim 1 wherein there are two such blocks provided, one between each of the said two walls and the stack, whereby air is withdrawn horizontally across the stack and then directed downwardly to the vacuum chamber at the sides of the stack adjacent the said two walls.

3. The improvement defined in claim 2 wherein the air-impervious cover comprises a thin plastic sheet spread across the stack and over the said two blocks and the said two walls at the said sides of the stack.

4. The improved apparatus of claim 3 and wherein the means associated with the cover to permit generally horizontal air flow and the two blocks are combined as a single relatively flexible and non-compressible pad of air-pervious material extending across the stack below the plastic cover sheet and in the direction thereof and then downwardly at the sides of the stack between it and the said two walls.

5. The stack supporting apparatus set forth in claim 3 wherein the said means associated with the cover comprises a relatively non-compressible blanket extending across the stack and onto the two blocks at the sides thereof below the plastic cover sheet the said blanket being corrugated at least on its bottom face to define flutes extending across the stack to accommodate the generally horizontal flow of air.

6. The stack supporting apparatus as defined in claim 1 and wherein there are two generally vertical impervious walls, each at a side of the stack opposite the other and projecting upwardly from the base approximately to the height of the stack, there are two relatively noncompressible air-pervious blocks, each at a side of the stack between the stack and the adjacent vertical wall, and wherein the cover and the air flow permitting means associated therewith comprise a relatively noncompressible blanket which extends across the stack and the two blocks with its side edges resting on the upper ends of the two vertical walls, the said blanket being corrugated at least on its bottom face to define flutes which are closed at their ends adjacent the side edges of the blanket to accommodate the generally horizontal flow of air from the stack onto the said blocks.

7. The stack supporting apparatus of claim 1 wherein there are two generally vertical impervious walls, each at a side of the stack opposite the other and projecting upwardly from the base approximately to the height of the stack, there are two relatively non compressible air-pervious blocks, each at a side of the stack between the stack and the adjacent vertical wall, and wherein the cover and air flow permitting means associated therewith comprise a pair of flexible but relatively noncompressible impervious endless belts, and means supporting said endless belts for generally horizontal movement relative to the base on opposite sides of the said tool and with the lower extent of thebelts engaging the top of the stack and extending across the stack and the two blocks with the side edges of the belts over the two. vertical walls, the said belts being corrugated on their outer surfaces to define flutes whichare closed at their ends adjacent the side edges of thetbelts to accommodate the generally horizontal flow of air from the stack onto the said blocks.

8. The apparatus as defined in claim 7 wherein the means supporting the endless belts is movable with the,

tool relative to the base longitudinally of the said belts.

9. In an apparatus for supporting a stack of sheet material to be cut and having a horizontal longitudinally extending air-pervious base disposed between vertical impervious side walls to cover a chamber subjected to vacuum to draw air downwardly through the base and also having a carriage supporting a cutting tool for movement longitudinally and transversely relative to the base while the tool reciprocates vertically into the base to cut a stack supported on the base, an improved structure for subjecting a stack having impervious sheets to the vacuum force including an air-pervious block disposed between the stack and each side wall, an air impervious cover extending across the stack and between the side walls, means associated with said cover adjacent the top of the stack to permit air flow transversely of the stack into the air-pervious blocks,

and means supported by the carriage to engage said cover adjacent the reciprocating cutting tool and movable longitudinally and transversely with the cutting tool to minimize the loss of vacuum force caused by the tool cutting the cover with the stack.

10. The apparatus as set forth in claim 9 wherein the last mentioned means comprises a pair of rotatably supported rollers which engage the cover on opposite transverse sides of the cutting tool and adjacent thereto.

11. The apparatus of claim 10 wherein a presser foot is associated with each such roller to assist in holding the cover down.

12. The apparatus as defined in claim 9 and further including a pair of impervious endless belts and means for rotatably supporting said endless belts on the carriage in engagement with said cover adjacent said cutting tool on opposite longitudinal sides thereof, the belts being supported by the carriage for movement relative to the base and stack in the longitudinal direction only.

13. An apparatus for supporting and holding in a rel atively firm condition a stack of sheet material including at least one relatively air-impervious layer, said apparatus comprising a base having a supporting surface upon which a stack of sheet materialsuchas aforesaid said supporting 'surface, means providing an airimpervious cover extending over the top of a stack of sheet material supported on said-supporting surface, a layer of material permitting horizontal airflow between said cover and the upper portion of said stack, and means adjacent at least one edge of said stack for con ducting, air from said horizontal air flow permitting layer to said supporting surface so that airis withdrawn from said horizontal air flow permitting layer by said vacuum adjacent said supporting surface 14. An apparatus as defined in claim 13 further characterized by said means for conducting air from said horizontal air flow permitting layer to said supporting surface comprising a block of porous material positioned adjacent said'at least one edge of said stack. 15. An apparatus as defined in claim 14 further characterized by said cover being a sheet of flexible airimpervious material which extends over said layer of material permittinghorizontal air flow and downwardly past the outboard side of said porous block to said supporting surface.

16. Apparatus as defined in claim 13 further characterized by said layer of material permitting horizontal air flow being a sheet of material having a surface configuration on its undersurface which provides air conducting channels between it and said stack of material.

17. An apparatus as defined in claim 13 further characterized by said means for conducting air from said layer of material permitting horizontal air flow to said supporting surface consisting of additional portions of said latter layer of material and of said cover which additional portions extend downwardly past said at least one edge of said stack of material from the top of said stack to said supporting surface.

18. An apparatus as. defined in claim 13 further characterized by said layer of material permitting horizontal air flow comprising corrugated cardboard.

19. An apparatus as defined in claim 13 further characterized by said supporting surface being divided into a plurality of zones arranged end-to-end longitudinally of said base and each extending transversely of said base, said means for providing said vacuum adjacent said supporting surface including means for selectively providing said vacuum at desired ones of said zones, and said layer of material permitting horizontal air flow having air conducting channels extending only generally transversely of said base.

20. In an apparatus for cutting a stack of sheet mate: rial comprised of a plurality of generally similar layers of sheet material superimposed on one another and including a means providing a supporting surface upon which a stack of sheet material such as aforesaid may be placed and also including a cutting tool and means for moving said stack and said cutting tool relative to one another to cause said cutting tool to follow a desired line of cut on said stack, an improved structure for subjecting said stack of sheet material to a vacuum force to hold it in a firm condition for cutting, said improved structure comprising anair-impervious cover extending over the top of said stack of sheet material, means other than one of said generally similar layers of sheet material of said stack providing air flow channels between said cover and the top layer of said stack, and means adjacent at least one edge of said stack for drawing air from said air flow channels to create a subatmol1 spheric pressure. on the underside of said cover whereby atmospheric pressure acting on the top side of said cover urges it toward said supporting surface to compress said stack.

21. An apparatus as defined in claim 20 further characterized by said air-impervious cover comprising a thin plastic cover sheet, and said means providing air flow channels between said cover and the top layer of said stack comprising a separate sheet of material interposed between said stack and said cover sheet.

22. An apparatus as set forth in claim 21 wherein said separate sheet of material is a sheet of corrugated cardboard.

23. An apparatus as defined in claim 20 further characterized by said cover having its under-surface configured to define said air flow channels between said cover and said top layer of said stack. a

24. An apparatus as defined in claim 20 further characterized by saidmeans for drawing air from said air flow channels including an elongated air conducting member extending along said at least one edge of said stack, and means for applying a vacuum to said elongated member.

25. An apparatus as defined in claim 24 further characterized by said elongated member being a block of porous material.

26. An apparatus as defined in claim 20 further char-- acterized by a pair of endless belts of air-impervious material located above said cover and on opposite sides of said cutting too], said belts each having a portion thereof engageable with said cover to seal cuts made in said cover by said cutting tool, and means supporting said belts for movement in response to movement of said cutting tool in one coordinate direction relative to said stack to maintain said belts in place relative to said cutting tool.

27. An apparatus as defined in claim 20 further characterized by a pair of rollers located on opposite transverse sides of said cutting tool and arranged to engage the top surface of said cover while said cutting tool is cutting to aid in holding down said cover.

28. An apparatus as defined in claim 20 further characterized by said cover being in the form of two endless belts of air-impervious sheet material located on opposite sides of said cutting tool and spaced from one another longitudinally of said supporting surface to form a transversely extending gap within which said cutting tool works, each of said endless belts of sheet material having its undersurface configured to define said air flow channels between said cover and said top layer of said stack. 

1. In an apparatus for supporting a stack of sheet material to be worked upon by a tool and having a generally horizontal airpervious base disposed between generally vertical impervious walls to cover a chamber subjected to vacuum to draw air downwardly through the base, and also having a means supporting a tool over the base for movement relative thereto when working upon a stack supported on the base, an improved structure for subjecting a stack having impervious sheet material to the vacuum force by withdrawing air horizontally from the stack and then downwardly, such structure including an air-impervious cover extending between at least two of the said walls and across the stack, means associated with the cover adjacent the top of the stack to permit generally horizontal air flow in the direction the cover extends across the stack, and an air-pervious block disposed between at least one of the said walls and the stack to permit the air being withdrawn horizontally of the stack to be directed downwardly to the vacuum chamber, whereby the stack is firmly supported on the base by air at atmospheric pressure bearing upon the cover.
 2. The apparatus improvement set forth in claim 1 wherein there are two such blocKs provided, one between each of the said two walls and the stack, whereby air is withdrawn horizontally across the stack and then directed downwardly to the vacuum chamber at the sides of the stack adjacent the said two walls.
 3. The improvement defined in claim 2 wherein the air-impervious cover comprises a thin plastic sheet spread across the stack and over the said two blocks and the said two walls at the said sides of the stack.
 4. The improved apparatus of claim 3 and wherein the means associated with the cover to permit generally horizontal air flow and the two blocks are combined as a single relatively flexible and non-compressible pad of air-pervious material extending across the stack below the plastic cover sheet and in the direction thereof and then downwardly at the sides of the stack between it and the said two walls.
 5. The stack supporting apparatus set forth in claim 3 wherein the said means associated with the cover comprises a relatively non-compressible blanket extending across the stack and onto the two blocks at the sides thereof below the plastic cover sheet the said blanket being corrugated at least on its bottom face to define flutes extending across the stack to accommodate the generally horizontal flow of air.
 6. The stack supporting apparatus as defined in claim 1 and wherein there are two generally vertical impervious walls, each at a side of the stack opposite the other and projecting upwardly from the base approximately to the height of the stack, there are two relatively non-compressible air-pervious blocks, each at a side of the stack between the stack and the adjacent vertical wall, and wherein the cover and the air flow permitting means associated therewith comprise a relatively non-compressible blanket which extends across the stack and the two blocks with its side edges resting on the upper ends of the two vertical walls, the said blanket being corrugated at least on its bottom face to define flutes which are closed at their ends adjacent the side edges of the blanket to accommodate the generally horizontal flow of air from the stack onto the said blocks.
 7. The stack supporting apparatus of claim 1 wherein there are two generally vertical impervious walls, each at a side of the stack opposite the other and projecting upwardly from the base approximately to the height of the stack, there are two relatively non-compressible air-pervious blocks, each at a side of the stack between the stack and the adjacent vertical wall, and wherein the cover and air flow permitting means associated therewith comprise a pair of flexible but relatively non-compressible impervious endless belts, and means supporting said endless belts for generally horizontal movement relative to the base on opposite sides of the said tool and with the lower extent of the belts engaging the top of the stack and extending across the stack and the two blocks with the side edges of the belts over the two vertical walls, the said belts being corrugated on their outer surfaces to define flutes which are closed at their ends adjacent the side edges of the belts to accommodate the generally horizontal flow of air from the stack onto the said blocks.
 8. The apparatus as defined in claim 7 wherein the means supporting the endless belts is movable with the tool relative to the base longitudinally of the said belts.
 9. In an apparatus for supporting a stack of sheet material to be cut and having a horizontal longitudinally extending air-pervious base disposed between vertical impervious side walls to cover a chamber subjected to vacuum to draw air downwardly through the base and also having a carriage supporting a cutting tool for movement longitudinally and transversely relative to the base while the tool reciprocates vertically into the base to cut a stack supported on the base, an improved structure for subjecting a stack having impervious sheets to the vacuum force including an air-pervious block disposed between the stack and each side wall, an air impeRvious cover extending across the stack and between the side walls, means associated with said cover adjacent the top of the stack to permit air flow transversely of the stack into the air-pervious blocks, and means supported by the carriage to engage said cover adjacent the reciprocating cutting tool and movable longitudinally and transversely with the cutting tool to minimize the loss of vacuum force caused by the tool cutting the cover with the stack.
 10. The apparatus as set forth in claim 9 wherein the last mentioned means comprises a pair of rotatably supported rollers which engage the cover on opposite transverse sides of the cutting tool and adjacent thereto.
 11. The apparatus of claim 10 wherein a presser foot is associated with each such roller to assist in holding the cover down.
 12. The apparatus as defined in claim 9 and further including a pair of impervious endless belts and means for rotatably supporting said endless belts on the carriage in engagement with said cover adjacent said cutting tool on opposite longitudinal sides thereof, the belts being supported by the carriage for movement relative to the base and stack in the longitudinal direction only.
 13. An apparatus for supporting and holding in a relatively firm condition a stack of sheet material including at least one relatively air-impervious layer, said apparatus comprising a base having a supporting surface upon which a stack of sheet material such as aforesaid may be placed, means providing a vacuum adjacent said supporting surface, means providing an air-impervious cover extending over the top of a stack of sheet material supported on said supporting surface, a layer of material permitting horizontal air flow between said cover and the upper portion of said stack, and means adjacent at least one edge of said stack for conducting air from said horizontal air flow permitting layer to said supporting surface so that air is withdrawn from said horizontal air flow permitting layer by said vacuum adjacent said supporting surface.
 14. An apparatus as defined in claim 13 further characterized by said means for conducting air from said horizontal air flow permitting layer to said supporting surface comprising a block of porous material positioned adjacent said at least one edge of said stack.
 15. An apparatus as defined in claim 14 further characterized by said cover being a sheet of flexible air-impervious material which extends over said layer of material permitting horizontal air flow and downwardly past the outboard side of said porous block to said supporting surface.
 16. Apparatus as defined in claim 13 further characterized by said layer of material permitting horizontal air flow being a sheet of material having a surface configuration on its undersurface which provides air conducting channels between it and said stack of material.
 17. An apparatus as defined in claim 13 further characterized by said means for conducting air from said layer of material permitting horizontal air flow to said supporting surface consisting of additional portions of said latter layer of material and of said cover which additional portions extend downwardly past said at least one edge of said stack of material from the top of said stack to said supporting surface.
 18. An apparatus as defined in claim 13 further characterized by said layer of material permitting horizontal air flow comprising corrugated cardboard.
 19. An apparatus as defined in claim 13 further characterized by said supporting surface being divided into a plurality of zones arranged end-to-end longitudinally of said base and each extending transversely of said base, said means for providing said vacuum adjacent said supporting surface including means for selectively providing said vacuum at desired ones of said zones, and said layer of material permitting horizontal air flow having air conducting channels extending only generally transversely of said base.
 20. In an apparatus for cutting a stack of sheet material coMprised of a plurality of generally similar layers of sheet material superimposed on one another and including a means providing a supporting surface upon which a stack of sheet material such as aforesaid may be placed and also including a cutting tool and means for moving said stack and said cutting tool relative to one another to cause said cutting tool to follow a desired line of cut on said stack, an improved structure for subjecting said stack of sheet material to a vacuum force to hold it in a firm condition for cutting, said improved structure comprising an air-impervious cover extending over the top of said stack of sheet material, means other than one of said generally similar layers of sheet material of said stack providing air flow channels between said cover and the top layer of said stack, and means adjacent at least one edge of said stack for drawing air from said air flow channels to create a subatmospheric pressure on the underside of said cover whereby atmospheric pressure acting on the top side of said cover urges it toward said supporting surface to compress said stack.
 21. An apparatus as defined in claim 20 further characterized by said air-impervious cover comprising a thin plastic cover sheet, and said means providing air flow channels between said cover and the top layer of said stack comprising a separate sheet of material interposed between said stack and said cover sheet.
 22. An apparatus as set forth in claim 21 wherein said separate sheet of material is a sheet of corrugated cardboard.
 23. An apparatus as defined in claim 20 further characterized by said cover having its under-surface configured to define said air flow channels between said cover and said top layer of said stack.
 24. An apparatus as defined in claim 20 further characterized by said means for drawing air from said air flow channels including an elongated air conducting member extending along said at least one edge of said stack, and means for applying a vacuum to said elongated member.
 25. An apparatus as defined in claim 24 further characterized by said elongated member being a block of porous material.
 26. An apparatus as defined in claim 20 further characterized by a pair of endless belts of air-impervious material located above said cover and on opposite sides of said cutting tool, said belts each having a portion thereof engageable with said cover to seal cuts made in said cover by said cutting tool, and means supporting said belts for movement in response to movement of said cutting tool in one coordinate direction relative to said stack to maintain said belts in place relative to said cutting tool.
 27. An apparatus as defined in claim 20 further characterized by a pair of rollers located on opposite transverse sides of said cutting tool and arranged to engage the top surface of said cover while said cutting tool is cutting to aid in holding down said cover.
 28. An apparatus as defined in claim 20 further characterized by said cover being in the form of two endless belts of air-impervious sheet material located on opposite sides of said cutting tool and spaced from one another longitudinally of said supporting surface to form a transversely extending gap within which said cutting tool works, each of said endless belts of sheet material having its undersurface configured to define said air flow channels between said cover and said top layer of said stack. 